When using wireless LANs conforming to the IEEE 802.11 standard, users have to set wireless communication parameters, such as network identifiers (ESSID), encryption methods, cryptographic keys(encryption keys), authentication methods, authentication keys, etc. Because of the complexity of these setting operations, methods have been proposed for automatically performing them between terminals. For instance, a method for automatic transfer of wireless parameter settings between an access point (relay station) and a station (terminal) from the access point to the station by means of a simple operation, etc. has been implemented as an actual product.
Moreover, in recent years, communication is also more frequently conducted over so-called ad hoc networks, in which terminals communicate with one another directly over a wireless LAN without passing through an access point. The demand for communication between a plurality of terminals on such ad hoc networks is on the increase and methods for automatic setting of parameters on a plurality of terminals are required (see Patent document 1: U.S. Pre-Grant Publication No. 2002/147,819 (Japanese Patent Laid-Open No. 2002-359623)).
In conventional automatic parameter setting methods, a master device such as an access point, which operates as a master, has a set made up of a public key and a private key, and slave devices, which function as slaves, generate session keys. The setting of wireless parameters is initiated when the master device transmits a public key to the slave devices. Here, when the slave devices receive the public key, they encrypt session keys using the public key and transmit them to the master device.
On the other hand, when the master device receives a session key encrypted using the public key, it uses the private key for decryption. When the decryption is over, wireless parameters are encrypted using the session key and transmitted to the slave device. By doing so, when the slave device receives the wireless parameters encrypted using the session key, it uses the session key for decryption. When the decryption is over, the slave device acquires and sets wireless parameters. Therefore, processing (heavy-load processing) involving decrypting data encrypted with a public key using a private key corresponding to the public key has been performed by the master device.
However, when wireless communication parameters are set in a plurality of devices, no other processing can be performed simultaneously when the master device performs such processing, and therefore, master device functionality ends up being occupied by a single slave device. Therefore, other slave devices must wait until the processing by the master device is complete, and the time it takes for all the slave devices to complete wireless parameter setting is prolonged depending on the number of times the master device decrypts the session keys.